Unless you really really care about reliability, the Toyota is kind of in last place. The Tundra and Tacoma have proven to last to over 250k miles easily. In my opinion, the clear winner is the F-150. The new Silverado just isn't as good of a value as the F-150. The RAM 1500 is the most comfortable truck, but I would worry about reliability. The RAM is entirely new for 2019 and with the new technology comes a sacrifice in reliability.
Since you don't need all the bells and whistles, the Toyota might be the best choice for its reliability and standard safety features. If you do want the most modern features (you said you didn't) such as trailer parking assist and air suspension, the other options are all better. The 2008 and newer trucks are the best years.
For your need for rear seat space, the Tundra has about 4 inches less combined legroom than the three other trucks. Despite this, all the trucks with the double cab have a very spacious rear seat so that isn't too important to worry about.
This is more of a matter of test driving than anything else, but I think the Tundra and Tacoma are the best trucks to buy used. The regulars on TrueDelta including me don't own a truck, but we would love to hear what you end up buying and why.